The textbook "Welfare Economics" by Yew-Kwang Ng offers a comprehensive analysis of welfare economics and expands the discussion beyond traditional preference theory. Ng integrates the inframarginal analysis of labor division and argues for a redefinition of the foundations of public policy by shifting the focus from mere preferences to a concept of happiness. The book also addresses the theory of the third best and highlights the challenges in the tension between equality and efficiency. A key insight is the simplification of public policy formulation, particularly in cost-benefit analysis, by treating one dollar as equivalent to another. These approaches provide valuable perspectives for designing policies that promote the well-being of society.